Developer's messaging API guide: webhooks and events explained

If you're going to build on a messaging platform, sooner or later you hit two concepts: the REST API (your code calls the platform) and webhooks (the platform calls your code). This developer's messaging API guide explains how they fit together, which events matter, and how to implement a robust webhook receiver that doesn't drop messages.

REST API vs webhooks: direction matters

The fundamental difference is who initiates the communication:

• REST API (outbound push): your app makes an HTTP request to do something: send a message, create a contact, move a deal, list conversations. You control the when.
• Webhooks (inbound push): the platform sends you an HTTP POST when something happens: a message arrives, a delivery status changes, a conversation closes. You don't ask; you get notified.

Using polling (hitting the API every X seconds for updates) is inefficient and slow. Webhooks are the correct way to react in real time.

Anatomy of a webhook

A typical webhook event arrives as a POST with a JSON body. Its structure usually includes:

• An event or type identifying what happened (for example message.received, message.status, conversation.closed).
• A timestamp of when the event occurred.
• A data object with the payload: the message, the contact, the channel, the metadata.
• A signature in the headers (HMAC) to verify authenticity.

Your endpoint must respond quickly with a 200 OK. If you're slow or return an error, the platform will retry, and that's where problems start if you didn't design well.

Events you'll almost always want to listen for

While every platform has its own catalog, these are the baseline events of any serious conversational integration:

1. message.received — a customer message came in.
2. message.sent / message.status — your message was sent, delivered, read or failed.
3. conversation.created — a new thread started.
4. conversation.assigned — it was assigned to an agent or team.
5. conversation.closed — the conversation was closed.
6. contact.created / contact.updated — changes to the customer record.
7. deal.stage_changed / deal.won — movements in the sales pipeline.

Omnifox, for instance, exposes over 40 event types across messaging, CRM, workflows and calls, so you can subscribe only to what your integration needs instead of receiving everything.

How to build a robust receiver

These practices separate a toy integration from a production one:

• Always verify the signature. Compute the HMAC of the body with your secret and compare it to the header. Reject any POST that doesn't match; it's your only defense against forged webhooks.
• Respond fast, process later. Return 200 immediately and queue the heavy work. If you process synchronously and take too long, you'll cause retries and duplicates.
• Be idempotent. Webhooks can arrive more than once. Store the event ID and discard repeats so you don't create the same record twice.
• Handle ordering. Events don't always arrive in order. Use the event timestamp, not the receive time, to reconstruct the real sequence.
• Log and monitor. Log every webhook received with its ID and outcome. When something fails, you'll want to be able to replay it.
• Have a tolerant retry endpoint. Return 5xx only if you truly want a retry; returning 4xx usually marks the event as permanently failed.

Retries and queues: the detail that breaks integrations

Most platforms retry a failed webhook with exponential backoff for hours. This is good (you don't lose events) but dangerous if your logic isn't idempotent: each retry can duplicate a contact or fire an automation twice. The solution is always the same: receive -> verify signature -> respond 200 -> queue -> process with ID-based deduplication. With that pattern, neither a traffic spike nor a momentary server outage will make you lose or duplicate data.

Conclusion

Mastering webhooks and the REST API is what lets you build reactive, reliable messaging experiences: you react in real time, keep your systems in sync, and don't drop events. Verify signatures, be idempotent, respond fast and queue the heavy lifting; those four habits alone cover the vast majority of the problems teams hit in production. If you want a clean API with granular events and well-documented webhooks to start building today, explore Omnifox and connect your product to the conversation.